According to internet sources and my Chinese friend living in Japan, there isn't. However, can someone provide more evidence on this issue? If there is no grammatical distinction, how can we distinguish these two tenses? I mean, how do we know if one sentence is translated to "did something", while the other to "have done something"?
Edit: I have a new question but I am not sure to start a new one or add to this. My question is on the construction of english tenses in Japanese. I know there is no one-to-one correspondence. But I am hoping to reconstruct them as accurate as possible. Simple past is ta-form. Present perfect is もう plus た-form. Past perfect is もう plus ていた. Is this correct?